News Release Number: STScI-2010-07

Suspected Asteroid Collision Leaves Odd X-Pattern of Trailing Debris

February 2, 2010: Something awfully curious is happening 100 million miles
from Earth in the asteroid belt. There's a newly discovered
object that superficially looks like a comet but lives among the
asteroids. The distinction? Comets swoop along elliptical orbits close in to the Sun and grow long gaseous and dusty tails, as ices near the surface turn into vapor and release dust. But asteroids
are mostly in circular orbits in the asteroid belt and are not
normally expected to be "volatile."

The mystery object was discovered on January 6, 2010, by the
Lincoln Near-Earth Asteroid Research (LINEAR) sky survey. The
object appears so unusual in ground-based telescopic images
that discretionary time on NASA's Hubble Space Telescope was
used to take a close-up look. The observations show a bizarre
X-pattern of filamentary structures near the point-like nucleus
of the object and trailing streamers of dust. This complex
structure suggests the object is not a comet but instead the
product of a head-on collision between two asteroids traveling
five times faster than a rifle bullet. Astronomers have long
thought that the asteroid belt is being ground down through
collisions, but such a smashup has never before been seen.